With the continuous development of semiconductor technologies, semiconductor devices have been developed toward high integration level with high quality. The critical dimension (CD) of the semiconductor devices has been correspondingly reduced. Reducing the critical dimension of the semiconductor devices allows more transistors to be formed on one chip. Accordingly, the performance of the semiconductor devices is improved.
In the field of memory devices, with the development of information technologies, the amount of the information have been continuously increased. Accordingly, higher requirements for the capacity of the memory devices have been brought out. A memory device often includes a storage region and a peripheral region. The storage region is used to form memory cells; and the memory cells are used to store data. The peripheral region is used to form the peripheral circuits of the memory device. With the continuous shrinking of the sizes of the memory transistors, forming more transistors in the storage region has the great advantage to increase the amount of information stored in the memory device. The memory device has different requirements for the properties of the transistors in the storage region and the transistors in the peripheral region. Thus, the structures of the transistors in the storage region and the structures of the transistors in the peripheral region are different.
With the continuous shrinking of the sizes of the transistors in the storage region, the differences between the structures of the transistors in the storage region and the structures of the transistors in the peripheral region have become more obvious.
The transistors in the storage region and the transistors in the peripheral region can be fin field-effect transistors (FinFETs). During the process for forming the FinFETs, to reduce the electric field at the corners between the top surfaces and the side surfaces of the fins of the FinFETs, and to prevent the gate dielectric layer at the corner from being broken-down, an oxidation process is often performed on the fins to increase the radius of curvature of the fins. The requirements of the oxidation process on the storage region of the devices and the requirements of the oxidation process on the peripheral region of the devices are different.
However, it is difficult to match the difference between the requirements of the oxidation process on the storage region and the requirements of the oxidation process on the peripheral region. Thus, the performance of the semiconductor structure having the memory device is not as desired. The disclosed methods and semiconductor structures are directed to solve one or more problems set forth above and other problems in the art.